Glass fibers are produced by the attenuation of molten glass issuing from nozzles under the influence of gravity. The nozzles are normally contained in an array on a bushing plate.
A bushing plate is normally fabricated of a precious metal alloy, nominally 80% platinum and 20% rhodium, to be able to withstand the extremely high processing temperatures of glass and the presence of corrosive agents in the bushing environment. A bushing plate has a limited service life, and must be repaired or reclaimed for re-use of the precious metal alloy.
The productivity or throughput of a bushing plate is a function of the number of nozzle tips contained in the array on the plate. The nozzle tips must be formed with uniform bore dimensions, wall thicknesses and heights to ensure uniformity in the diameter of the resultant glass fibers. The bushing plate through its high material cost, limited service life and accuracy requirements is a significant component of the cost of capital equipment used in glass fiber production. The objective of the present invention is, therefore, to provide a bushing plate Which can be produced by a high-quality, low-cost process, and contains a relatively dense packaging of nozzle tips on the plate to accord a high commercial production of glass fibers.
A summary of known techniques for forming bushing plates is given in K. L. Loewenstein, The Manufacturing Technology Of Continuous Glass Fibers, 2nd Ed., pages 131-35, Elsevier Science Publishers B.V., The Netherlands. However, bushing plates made in accordance with the method of embossing one side of a sheet of material and cold forming the formed boss into a nozzle tip extending from the said one side results in a layered, high stress fillet where the nozzle is contiguous with the surface.